Trust Based System and Method for Performing a Handover from a Source Base Station to a Target Base Station

1. A method for performing a handover of a mobile terminal from a source base station to a target base station, the source and target base stations being adapted to directly communicate with each other via first respective communication interfaces, the source and target base stations being adapted to communicate via second respective communication interfaces with a core network entity, the core network entity managing subscriptions to services of at least the target base station and authorizing access to said services via handover to only subscribers to said services, said method comprising: obtaining a trust level indication for the mobile terminal, said trust level indication being representative of an extent to which the mobile terminal can be trusted when declaring having subscribed to the services of the target base station; performing directly the handover via the first communication interfaces, when the obtained trust level indication is above a first threshold; and otherwise requesting authorization from said core network entity for the mobile terminal to access via handover the services of the target base station.

2. The method according to claim 1 , wherein the trust level indication is determined as a function of a time period elapsed since a preceding modification of the trust level indication or since a preceding authorization from the core network entity for the mobile terminal to access via handover the services of the target base station.

3. The method according to claim 1 , wherein the trust level indication is determined as a function of a number of successive handovers performed by base stations by directly communicating with each other without requesting authorization from said core network entity and undergone by the mobile terminal to enter a cell managed by the source base station.

4. The method according to claim 1 , wherein the core network entity defines the first threshold on the basis of an offload policy of signalling from the core network toward base stations.

5. The method according to claim 1 , wherein the target base station defines or adjusts the first threshold for the source base station, on the basis of an access policy to the services of the target base station.

6. The method according to claim 1 , wherein the trust level indication is defined on the basis of at least one parameter weighted by at least one respective forgetting factor, and wherein: the at least one forgetting factor is adjusted by said core network entity on the basis of an offload policy of signalling from the core network toward base stations; or the at least one forgetting factor is adjusted by the target base station on the basis of an access policy to the services of the target base station.

7. The method according to claim 1 , wherein the target base station performs: receiving from the source base station a request to perform directly the handover via the first communication interfaces for the mobile terminal and receiving from the source base station said trust level indication; accepting to perform directly the handover via the first communication interfaces for the mobile terminal, when the trust level indication is above a first threshold; and otherwise requesting, via the second communication interface of the target base station, authorization from said core network entity for the mobile terminal to access via handover the services of the target base station.

8. The method according to claim 1 , wherein the core network entity performs, when the trust level indication is above the first threshold: instructing the source base station to perform directly, via the first communication interfaces, following handovers toward the target base station for the mobile terminal.

9. The method according to claim 8 , wherein the source base station performs, when detecting that the handover has to be performed toward the target base station for the mobile terminal: performing the handover via its first communication interface, when instructed by the core network entity to perform directly, via the first communication interfaces, handovers toward the target base station via the first communication interfaces for the mobile terminal; and otherwise requesting, via the second communication interface of the source base station, authorization from said core network entity for the mobile terminal to access via handover the services of the target base station.

10. The method according to claim 8 , wherein the core network entity performs, when the trust level indication is below or equal to the first threshold: instructing the source base station to stop performing directly, via the first communication interfaces, following handovers toward the target base station for the mobile terminal.

11. The method according to claim 8 , wherein the source base station performs, when detecting that the mobile terminals enters a cell managed by the source base station: obtaining a number of successive handovers performed by base stations by directly communicating with each other without requesting authorization from said core network entity and undergone by the mobile terminal to enter the cell managed by the source base station; and, when detecting that the handover has to be performed toward the target base station for the mobile terminal: performing directly the handover via its first communication interface, when said number of successive handovers is below a second threshold, independently of being instructed by the core network entity to perform directly, via the first communication interfaces, following handovers toward the target base station for the mobile terminal; and otherwise requesting, via the second communication interface of the source base station, authorization from said core network entity for the mobile terminal to access via handover the services of the target base station.

12. The method according to claim 1 , wherein said method is performed by the source base station.

13. The method according to claim 12 , wherein, when the handover is performed directly via the first communication interfaces, the source base station transmits to the target base station a mobile terminal context including the trust level indication and/or a number of successive handovers performed by base stations by directly communicating with each other without requesting authorization from said core network entity and undergone by the mobile terminal to enter a cell managed by the source base station.

14. The method according to claim 1 , wherein requesting authorization from said core network entity for the mobile terminal to access via handover the services of the target base station is performed when performing the handover via the second communication interfaces.

15. A system for performing a handover of a mobile terminal from a source base station to a target base station, the source and target base stations being adapted to directly communicate with each other via first respective communication interfaces, the source and target base stations being adapted to communicate via second respective communication interfaces with a core network entity, the core network entity managing subscriptions to services of at least the target base station and authorizing access to said services via handover to only subscribers to said services, said system comprising: means for obtaining a trust level indication for the mobile terminal, said trust level indication being representative of an extent to which the mobile terminal can be trusted when declaring having subscribed to the services of the target base station; means for performing directly the handover via the first communication interfaces, when the obtained trust level indication is above a first threshold; and otherwise means for requesting authorization from said core network entity for the mobile terminal to access via handover the services of the target base station.